Yarn Braking Body

ABSTRACT

A yarn braking body is a flexible frustocone coat made from plastic material and has a circumferentially continuous braking surface which is defined by a part of the inner surface of the frustocone coat. The yarn braking body has a circumferentially continuous support part at the small diameter end. The support part is spherical and one piece with the frustocone coat and is made from the plastic material of the yarn braking body such that the centre of the sphere lies in the axis of the frustocone coat which axis is prolonged beyond the large diameter end.

The invention relates to a yarn braking body according to the preambleof claim 1.

In knitting yarn feeding devices which are known in practice a yarnbraking body is implemented which is a precise frustocone coat made fromsmooth vacuum-shaped plastic material. The support part is a supportring firmly gripping the small diameter end of the frustocone coat andis installed as a separate part which comprises anchoring openingsserving to hook in tension springs which extend radially outwardly fromthe support part and which hold the braking body in the coaxialoperational position in contact with the rounded withdrawal rim of thestorage body of the knitting yarn feeding device. The holdingconstruction with the tensioning springs is structurally complicated.Manufacturing and assembling the support part at the yarn braking bodyneeds several working steps. The knitting yarn runs off the storage bodyover the withdrawal rim and along the yarn braking surface at the innerside of the frustocone coat and at the same time rotates like the handof a clock while it is pulled off axially through the small diameterend. The tension springs allow a certain movability of the yarn brakingbody and centre the yarn braking body on the withdrawal rim of thestorage body. The yarn braking body is a wear part which in some caseshas to be replaced relatively frequently. Due to the holdingconstruction replacements are time consuming. The support part increasesthe mass of the braking body.

It is an object of the invention to provide a yarn braking body of thetype as mentioned at the beginning which has low mass, can bemanufactured for fair costs, and which can be replaced and centredeasily.

This object is achieved by the features of claim 1.

Since the support part is integrated as one piece into the frustoconecoat the support part can be formed for fair costs during manufacturingthe yarn braking body. The spherical support part is laid then with itsspherical outer surface into a matching spherical pan for supporting thebraking body. The support part is held by the contact pressure at thewithdrawal rim of the storage body, and is centred by the spherical pan.The spherical support part forms so to speak a part of a spherical jointor a universal joint, respectively, which properly centres the yarnbraking body on the withdrawal rim of the storage body. The yarn brakingbody can easily be replaced. The integrated spherical support part doesnot increase the mass of the braking body and also does notsignificantly influence the radial deformability of the frustocone coatin the region of the braking surface. The easily shapeable plasticmaterial is used in order to form the spherical support part integrallywith the frustocone coat. The rigidity of the support part which isslightly increased by the spherical form is sufficient for a stablesuspension of the yarn braking body in the spherical pan withoutadditional reinforcement measures.

Expediently, the same wall thickness is present in the yarn braking bodyin the frustocone coat and in the spherical support part. The wallthickness e.g. amounts to between 0.2 mm and 0.5 mm. In this way theyarn braking body can be manufactured from a simple blank.Alternatively, it is possible to provide, at least regionally, adifferent wall thickness in the support part than in the frustoconecoat.

The sphere radius of the spherical support part may be designed suchthat it reacts in an expedient relationship with the diameter at thelarge diameter end of the yarn braking body. The sphere radius e.g. mayamount to between about 30% to 60% of the diameter. By this measure alarge contact surface is achieved in the ball joint while the radialdeformability of the frustocone coat is not significantly influenced inthe region of the braking surface.

The wall thickness expediently is smaller than 1.0 mm, preferably evensmaller than 0.5 mm. In case of a yarn braking body having a diameter ofabout 150 mm at the large diameter end the wall thickness may be about0.3 mm.

The cone angle of the regular frustocone coat should amount to betweenabout 100° and about 130°. Expediently, the cone angle amount to 120°.

The plastic material from which the yarn braking body is made should bea thermoplast, e.g. a polyester, PET or PVC. Such materials can beshaped easily and allow to achieve high durability and excellent surfaceproperties.

The yarn braking body expediently is made by, preferably thermal, vacuumshaping from a blank. In this case the blank even could be a planarblank. At least the die surface used when shaping the inner surface ofthe braking body in the region of the braking surface should be polishedin order to produce an inner surface in the yarn braking body which istruly smooth.

In order to achieve a uniform deformation property in the yarn brakingbody the spherical support part should continue the frustocone coatwithout a transition or a step. The spherical curvature, so to speak, isnestled into the frustocone.

The height dimension of the spherical support part measured in thedirection of the axis of the frustocone coat should measure betweenabout 15% to 35%, preferably less than 30%, of the height dimension ofthe yarn braking body.

By the integration of the spherical support part into the frustoconecoat the spherical support parts constitutes the small diameter end ofthe frustocone coat through which small diameter end the yarn will bewithdrawn. The yarn may be withdrawn directly through the support partor, alternatively, with the help of a yarn eyelet which is placed atthis location with or without a connection or a bonding to the yarnbraking body.

The outer diameter of the spherical support part should amount to about2.5 to 4.5 fold of the inner diameter of the smaller diameter end.Alternatively, the outer diameter of the spherical support part couldamount to between about 25% and 45% of the diameter of the largediameter end. In this fashion a sufficiently large contact surface isachieved in the ball joint.

The inner surface of the frustocone coat, at least in the region of thebraking surface, should have a smoothness which corresponds with apolished surface.

An embodiment of the invention is explained with the help of FIG. 1which in the left half is a side view of a yarn braking body and in theright half is a radial section of the yarn braking body.

A yarn braking body B in FIG. 1, expediently for a not shown knittingyarn feeding device, is provided for a co-action with a roundedwithdrawal rim of a drum-shaped storage body of a knitting yarn feedingdevice, in order to actuate or load the yarn with a relatively lowbraking force while the yarn is withdrawn inwardly over the withdrawalrim and at the same time is rotating like the hand of a clock. For thisreason, the yarn braking body is laid coaxially with the storage bodyfrom the front side against the withdrawal rim and is held in asuspension such that it is centred at the withdrawal rim butnevertheless remains somewhat movable. The yarn braking body B is aone-piece plastic material shaped part, e.g. made from a thermoplasticmaterial P like polyester, PET or PVC. The yarn braking body B e.g. ismanufactured by vacuum shaping on a forming die, in some cases even bythermal vacuum shaping.

The yarn braking body B consists of a regular frustocone coat K and aspherical support part S which is integrated in one piece into thefrustocone part K. The yarn braking body B has a large diameter circularend 1 having an opening 5 of a diameter D and a small diameter circularend 2 with an opening 4 of an inner diameter d. The frustocone coat Khas a linear generatrice 3 and an axis Y. The spherical support part Sis a stepless continuation of the generatrice 3 and has a sphere radiusR e.g. between 30% to 60% of the diameter D. The centre Z of the sphereis situated on the axis Y of the frustocone coat K which axis Y isprolonged beyond the large diameter end 1.

In a concise embodiment of a yarn braking body B with a diameter D ofabout 110 mm and a cone angle α of 120° the sphere radius R is about 590mm.

The wall thickness x of the yarn braking body B is the same in thefrustocone coat K and in the spherical support part S and amounts tobetween 0.2 mm and maximally 1.0 mm, preferably amounts to about 0.3 mm(in the case of a yarn braking body having a diameter D of 150 mm).Alternatively, the wall thickness in the spherical support part at leastin part could be different from the wall thickness in the frustoconecoat K.

The respective edges in the openings 5, 6 in the large diameter end 1and in the small diameter end 2 could be rounded. The inner surface ofthe frustocone coat constitutes at least in a region a ring-shaped,circumferentially continuous braking surface F. At least in the regionof the braking surface F the inner surface should be very smooth, e.g.with a smoothness corresponding to a polished surface.

The height h of the yarn braking body B in direction of the axis Y e.g.amounts in case of a diameter D of 110 mm to about 46 mm. The height h2of the spherical support part S amounts to somewhat less than 30% of theheight h and may amount to between about 15% to about 35% of the heighth. The outer diameter dS of the spherical support part S amounts toabout 2.5 to 4.5 fold of the inner diameter d of the small diameter end2, or may be about 25% to 45% of the diameter D, respectively. The coneangle α in general may amount to between about 100° and 135°. A tangentdrawn at the edge 6 of the opening 4 along the outer side of thespherical support part S either may be perpendicular to the axis Y ormay include an angle with the axis Y which angle is smaller than 90°.The height h1 of the frustocone coat K in each case is larger than theheight h2 of the spherical support part S. In no case should the yarnbraking surface F reach towards the spherical support part S.Expediently, the outer surface of the spherical support part S also hasa smoothness which corresponds to a polished surface.

1. Yarn braking body for a yarn feeding device, in particular for aknitting yarn feeding device, the yarn braking body being a flexiblefrustocone coat made from plastic material and having a large diameterend of substantially circular form, a small diameter end ofsubstantially circular form and a circumferentially continuous brakingsurface defined by a part of the inner surface of the frustocone coat,and having a circumferentially continuous support part at the smalldiameter end, wherein the support part is integrally made spherical andin one piece with the frustocone coat from the plastic material of theyarn braking body such that the center of the sphere lies in the axis ofthe frustocone coat which axis is prolonged beyond the large diameterend.
 2. Yarn braking body as in claim 1, wherein the wall thickness ofthe yarn braking body is continuously the same in the frustocone coatand in the spherical support part.
 3. Yarn braking body as in claim 1,wherein the sphere radius of the spherical support part is between30%,and 60%, preferably about 43%, of the diameter of the large diameterend of the frustocone coat.
 4. Yarn braking body as in claim 2, whereinthe wall thickness is smaller than 1.0 mm, preferably is between 0.2 mmand 0.5 mm.
 5. Yarn braking body as in claim 1, wherein the cone angleof the frustocone coat amounts to between about 100° and 135°.
 6. Yarnbraking body as in claim 1, wherein the plastic material is a thermalplastic material, e.g. polyester, PET or PVC.
 7. Yarn braking body as inclaim 1, wherein the yarn braking body is shaped by, preferably thermal,vacuum shaping of a blank, preferably of a planar blank.
 8. Yarn brakingbody as in claim 1, wherein the spherical support part is a steplesscontinuation of the frustocone coat.
 9. Yarn braking body as in claim 1,wherein the height of the spherical support part measured in thedirection of the axis of the frustocone coat measures between about 15%to 35%, preferably less than 30%, of the height of the yarn brakingbody.
 10. Yarn braking body as in claim 1, wherein the spherical supportpart forms the small diameter end of the frustocone coat.
 11. Yarnbraking body as in claim 1, wherein the outer diameter of the sphericalsupport part amounts to about 2.5 to 4.5 fold of the inner diameter ofthe small diameter end.
 12. Yarn braking body as in claim 1, wherein theouter diameter of the spherical support part amounts to about 25% to 45%of the diameter of the large diameter end.
 13. Yarn braking body as inclaim 1, wherein the inner surface of the frustocone coat has asmoothness at least in the region of the braking surface correspondingto a polished surface.